Angioedema is a clinical symptom reported to affect at least 20% of the population. It is readily recognized as a usually asymmetrical, non-erythematous, non-pruritic, non-pitting, localized, transient, episodic swelling of a soft body area involving lax skin, oropharyngolaryngeal tissue and/or gastrointestinal wall (Beltrani V. S. 2004: Angioedema: some new thoughts regarding idiopathic angioedema. In Urticaria and angioedema (Greaves, M. W., and A. P. Kaplan editors) pp. 421-439). The presence or absence of chronic recurrence of urticaria is a feature, which distinguishes the different forms of angioedema. Acute angioedema is frequently a direct consequence of the exposure to a specific substance (usually food, chemicals or drug) eliciting an allergic/pseudoallergic reaction, which releases histamine. Also, chronic recurrent angioedema, occurring with prominent urticarial flare, is typically histamine mediated. In contrast, for chronically recurrent angioedema without urticaria, the specific angioedema triggering is only vaguely described even when a predisposing condition is clearly identified. This situation is best illustrated in angioedema due to inherited C1-INH deficiency and in angioedema related to ACE inhibitor treatment. In spite of a lifelong stable C1-INH deficiency or of a continuous ACE inhibitor treatment, patients with these conditions are only occasionally symptomatic, with substantial variation in frequency and severity of symptoms.
The plasma kinin-forming pathway consists of three essential proteins that interact in vivo in a complex fashion once bound to a macromolecular complex formed during inflammatory response or bound to proteins along cell surfaces (Kaplan A. P., 2004. Mechanisms of bradykinin generation. In Urticaria and angioedema (Greaves, M. W. and A. P. Kaplan editors) (Marcel Decker Inc. New York) pp 51-72). These are coagulation factor XII [FXII (or Hageman Factor, HF)], prekallikrein (PK), and high molecular weight kininogen (HK). Once factor XII is activated to factor XIIa, it converts prekallikrein to kallikrein and the latter in turn digests HK to generate bradykinin. Factor XIIa has a second substrate in plasma; namely, coagulation factor XI and activation of surface bound factor XI by factor XIIa initiates the intrinsic coagulation pathway. Thus, the assembly and interactions of all four of these proteins are known as contact activation and the formation of bradykinin is therefore a cleavage product of the initiating step of the cascade (Kaplan, A. P. 2004. Mechanisms of bradykinin generation. In Urticaria and Angioedema, Greaves, M. W. and A. P. Kaplan editors, Marcel Decker Inc. New York, pp. 51-72). There is also a tissue pathway by which bradykinin is generated in which there is intracellular conversion of prekallikrein to tissue kallikrein by enzymes that are yet to be identified. Tissue kallikrein is secreted into the local milieu where it digests low molecular weight kininogen (LK) to generate lysyl-bradykinin (kallidin) and an amino-peptidase converts kallidin to bradykinin. The bradykinin that is produced by either pathway is then degraded by plasma enzymes as well as enzymes that are active along the surface of endothelial cells—particularly pulmonary vascular endothelial cells—to lower-molecular-weight peptides (Kaplan, 2004).
Bradykinin acts on the B2 receptor on the surface of the endothelial cells to cause vasodilatation and this in turn is enhanced by secondary production of vasodilators such as nitric oxide (NO) following stimulation of B2 receptors (Regoli & Barabe. 1980. Pharmacol. Rev. 32:1-46). In addition to its significant contribution to the inflammatory processes, the kinin-generating pathway has been implicated in various other physiological and pathophysiological processes including hypotension, tumor angiogenesis, and pain.
HK circulates in plasma as a 115 kDa non-enzymatic glycoprotein with a concentration of 70-90 μg/ml. Theoretically, there is sufficient concentration of HK in plasma to form non-covalent complexes with the two substrates of factor XIIa—prekallikrein and factor XI—thus leaving 10-20% of circulating HK uncomplexed. The attachment of prekallikrein or factor XI to HK occurs within the C-terminal region of HK, corresponding to the light chain that results after cleavage to release bradykinin. Earlier experiments have shown that the binding of HK to HUVECs (Kd 40-50 nM) is strictly zinc-dependent (25-50 mM), saturable, and reversible with an estimated 1×106 binding sites/cell. Furthermore, these experiments had shown that binding is with both the heavy and light chains of HK. Since there is apparently no separate site for prekallikrein, the prekallikrein-HK complex is brought to the endothelial cell surface by virtue of HK binding. When the binding of factor XII was studied, it was found to have binding characteristics strikingly similar to those seen with HK including a similar requirement for zinc. Subsequently, it was shown that HK and factor XII could compete for the same binding site at a comparable molar ratio suggesting that they compete for binding to the same or overlapping receptor sites.
Three endothelial cell binding sites for HK and factor XII have been described to date. These include gC1q-R, cytokeratin-1 (Hasan, et al., 1998. Proc. Natl. Acad. Sci. U.S.A. 95: 3615-3620; Joseph et al. 1999. Clin. Immunol. 92:246-255), and the urokinase plasminogen activator receptor (u-PAR) (Colman et al. 1997. J. Clin. Invest. 100:1481-1487). The binding of HK and factor XII to each of these proteins is zinc-dependent.
The HK binding site on gC1q-R has been identified on the C-terminal half corresponding to residues 204-218 (Ghebrehiwet et al. 1994. J. Exp. Med. 179:1809-1821; Ghebrehiwet et al. 2002. Immunobiol. 205:421-432. gC1q-R binds specifically to domain 5 in the light chain of HK but not to the heavy chain (Hasan et al. 1995. J. Biol. Chem. 270: 19256-19261; Herwald et al. 1996. J. Biol. Chem. 271:13040-13047). Domain 5 of HK, located within the N-terminus of the light chain, is rich in histidine and arginine residues and contains the site for interaction with gC1q-R. A 20 amino acid polypeptide termed HKH20 has been shown to be the site for attachment within domain 5 and this polypeptide can be used to inhibit the interaction of HK with intact endothelial cells (Hasan et al. 1995. J. Biol. Chem. 270: 19256-19261). The other site for attachment of HK to endothelial cells is found within domain 3 on the heavy chain, and a polypeptide containing the binding site, designated LDC27 has been identified. However, its binding affinity is approximately 100-fold less than the light chain (Herwald et al. 1995. J. Biol. Chem. 270:14634-14642).
The second endothelial cell-binding site for HK is cytokeratin 1. Like gC1q-R, this protein was isolated from cell membranes employing affinity chromatography with HK or LDC27 as ligand. Cytokeratin 1 therefore represents a major site of interaction for the HK heavy chain; although it is also capable of binding the light chain as well.
A third cell membrane constituent capable of binding HK is u-PAR, since antibody raised against u-PAR can inhibit cell membrane interaction with HK, and HK can bind to purified u-PAR in a zinc-dependent manner. Although purification of u-PAR using HK has not been successful, affinity chromatography using factor XII as ligand leads to purification of u-PAR rather selectively, with only traces of gC1q-R and cytokeratin-1 (Joseph et al. 2004. J. Thromb. Haemost. 91:61-70). Thus u-PAR may represent an important ligand for interaction with factor XII, while gC1q-R and cytokeratin-1 predominate in terms of HK binding. Because antibody to gC1q-R can immunoprecipitate gC1q-R and cytokeratin 1 but not u-PAR, and antibody to u-PAR can immunoprecipitate u-PAR and cytokeratin 1, but not gC1q-R, these molecules may reside on the membrane as closely associated bimolecular complexes of gC1q-R-cytokeratin-1 and u-PAR-cytokeratin-1 or as a trimolecular complex of gC1q-R-cytokeratin-1-u-PAR as was originally proposed (Joseph et al.; Mandi et al. 2001. Blood. 97:2342-2350; Mandi, et al. 2002. Hemost. Thromb. Vasc. Biol. 99:3585-3596).
Bradykinin and related kinins have been shown to induce vasodilatation and vascular permeability (Regoli & Barabe, 1980; Pharmacol. Rev 32: 1-46). When injected into humans and animals, bradykinin reproduces the cardinal signs and symptoms of inflammation, namely redness, local heat, swelling, and pain. Redness depends on endothelium-mediated vasodilatation, swelling from the contraction of capillary endothelia with the resulting opening of pores in the capillary filter, and pain from the stimulation of sensory fibers (Regoli & Barabe, 1980).
The biological effects of the kinins, including the stimulation of prostaglandin release, are mediated by two G-protein coupled receptors (GPCR) named B1 and B2 (Regoli & Barabe), which depending on the cell type in which they are expressed, promote the release of secondary mediators such as NO, PGI2, histamine and various neurotransmitters—all vasodilators and proinflammatory. Biological effects mediated by B1 and B2 receptors are linked to intracellular accumulation of Ca2+, cAMP, or cGMP. Whereas B2 receptors are constitutive, B1 receptors are inducible (by IL-1β, TNFα,) in pathological states.
The bradykinin that is produced during contact activation in vivo is degraded by plasma enzymes, as well as enzymes that are active along the surface of endothelial cells (particularly pulmonary vascular endothelial cells), to lower-molecular-weight peptides (Kaplan 2004). The major plasma enzyme is carboxypeptidase N, which removes the C-terminal arginine from bradykinin to yield an eight amino acid peptide, des-arg-9 bradykinin. The second kininase in plasma is termed kininase II, which predominates along the pulmonary vascular endothelial cell surface, and is identical to angiotensin-converting enzyme (ACE) (Yang, H Y T, Erdos, E G, 1967, Nature, 2151402-1403). This enzyme removes the dipeptide phe-arg from the C-terminus of bradykinin to yield a heptapeptide and a second cleavage removes ser-pro to leave a pentapeptide. Thus, bradykinin is controlled as soon as it is generated unless a condition(s) is created that favor its prolonged circulation in plasma. ACE inhibitors reduce catabolism of bradykinin.
The receptor for the globular heads of C1q, gC1q-R, is a ubiquitous, highly anionic cellular protein of 33 kDa that was identified and characterized as a cell-surface molecule that binds the globular heads of C1q (gC1q) (Ghebrehiwet et al. 1994. J. Exp. Med. 179: 1809-1821.-3). Known alternatively as p33, and sometimes as p32 or HABP-1 (hyaluronic acid binding protein I), it is now clear that it is also, and in fact predominantly, a protein of the mitochondrial matrix. In addition, it is distributed in several other cellular compartments, including the ER, and the nucleus, in addition to the cell surface (Ghebrehiwet et al. 1994. J. Exp. Med. 179: 1809-1821; Mandi et al. 2001. Blood. 97:2342-2350; Mandi et al. 2002. Hemost. Thromb. Vasc. Biol. 99:3585-3596). Binding of C1q to cells is known to induce and modulate a number of C1q-mediated cellular responses including inositol-trisphosphate (IP3) production in, expression of P-selectin on, and generation of procoagulant activity on, platelets; activation and expression of the adhesion molecules E-selectin, ICAM-1 and VCAM-1; and production of IL-6, IL-8, and monocyte chemoattractant protein-1 (MCP-1) on endothelial cells (ECs). Some of these functions have been shown by antibody inhibition to directly involve gC1q-R and/or the receptor for the collagen-like domains of C1q, cC1q-R/CR. In addition, gC1q-R in association with u-PAR and cytokeratin 1, is a high-affinity site for HK (Colman et al. 1997. J. Clin. Invest. 100:1481-1487; Hasan, et al. 1998. Proc. Natl. Acad. Sci. U.S.A. 95: 3615-3620).
One of the major side effects of patients on ACE inhibitors is angioedema (Agah et al. 1999. Intensive Care Med 23: 793-796; Agostoni et al. 1999. Immunopharmacology 15:21-25). ACE inhibitor-mediated angioedema has been reported to occur in 0.1-5.0% of patients, being five times more common in Afro-Caribbean Americans, and appears to be indistinguishable from any other form of angioedema. This type of angioedema, whose features include odynophagia (retrosternal pain with swallowing), swelling of the tongue, and potentially lethal laryngeal edema, has been reported to be a frequent cause (17-38%) of acute angioedema in referral centers today (Agah et al. 1999. Intensive Care Med 23: 793-796; Agostoni et al. 1999. Immunopharmacology 15:21-25). The present invention provides methods for treating and/or preventing angioedema and vascular permeability by interfering primarily with the interaction of HK with gC1q-R, and secondarily with the interaction of C1q with gC1qR.